1. Field of the Invention
This invention relates to mobile radio telephones and a private network system in which a plurality of private branch exchanges (PBXs), each switching the mobile radio telephones, are installed so as to enable originating connection of one exchange and terminating connection of another exchange in the office area of the PBX if a single mobile radio telephone is moved to any PBX in the private network.
2. Description of Related Art
FIG. 9 shows the configuration of a conventional radio telephone switching system in which a plurality of private branch exchanges (PBXs) are installed for connection to each other as an in-house network. In FIG. 9, PBX100 includes one or more radio connection controllers RC110, one or more radio termination interfaces RIF104, one or more ordinary telephones TEL109, one or more ordinary telephone terminal interfaces LIF105, one or more public telecommunication network interfaces COT106, and one or more in-house network interfaces TRK107 and TRK108. Further, the PBX100 includes a speech path switch SW103, a central controller or central processor CP101, and a memory MEM102. The switch SW103 is controlled by the central processor CP101. Data required for the central processor CP101 to control connection is stored in the memory MEM102. Other private branch exchanges PBX200 and PBX300 are of the same configuration.
In FIG. 9, the public telecommunication network interface COT106 is an interface for communication via a public telecommunication network and the in-house network interfaces TRK107 and TRK108 are interfaces with PBX200 and PBX300 respectively. The ordinary telephone TEL109, mobile radio telephones, etc., are assigned numbers indicating their respective identification codes and the correspondence between the identification codes and the interfaces through which the telephones having the identification codes are connected to the PBX100 are previously stored in the memory MEM102 of the PBX100.
In FIG. 9, in addition to the ordinary telephone TEL109, mobile radio telephones such as RT111 and RT112 can be connected via the radio connection controller RC110 and the radio termination interface RIF104 to the PBX100 for switching. When receiving a radio signal from a mobile radio telephone, the radio connection controller RC110 sends it via the radio termination interface RIF104 to the PBX100; when receiving a call signal from the PBX100, the radio connection controller RC110 converts it into a radio signal and sends the resultant signal to the corresponding mobile radio telephone. The radio connection controller and mobile radio telephones can communicate with each other at specific frequencies within the PBX service area. Their respective power is defined to reach in a predetermined range, for example, within 100 m, and each mobile radio telephone communicates with a near radio connection controller within the service area. For the PBX100 to perform radio connection control, it is necessary to manage which radio connection controller RC each mobile radio telephone RT is positioned near. This is referred to as position registration management. The position registration management registers and updates information as to which radio connection controller RC each mobile radio telephone RT is positioned near within the PBX. The mobile radio telephones are managed in the home office which is one of PBXs (in this case, PBX100). In the conventional system example given above, each mobile radio telephone can be combined with any desired radio connection controller for connection within the specific PBX. Thus, although a mobile radio telephone is moved anywhere, if a radio connection controller is located near the mobile radio telephone, the radio connection controller can be used for originating connection and terminating connection. That is, the positional relationships between the mobile radio telephones and radio connection controllers are registered for management in the home office to enable originating connection and terminating connection.
However, since only registration of the positional relationships within the single PBX is managed in the conventional system example given above, originating connection and termination connection cannot be made if mobile radio telephones are moved to the service area of a PBX other than the PBX where the positional relationships are registered. That is, information on movement of the mobile radio telephones is not transferred between the PBXs and thus the mobile radio telephones can be used only within the service area of the home office.